Synthetic elastomeric filaments from (a) polyester diols, (b) aliphatic or cycloaliphatic diols and (c) aliphatic or cycloaliphatic diisocyanates



United States Patent- Ofilice 3,357,954 Patented Dec. 12, 1967 ABSTRACTOF THE DISCLOSURE A process for the manufacture of syntheticpolyesterurethane elastomers capable of being melt-spun into filaments,comprising bringing about by the application of heat an interactionbetween (1) a diol whch is a hydroxylterminated linear copolyesterderivable from one or more aliphatic or cycloaliphatic glycols havingfrom 2 to 20 carbon atoms, and adipic acid optionally together with oneor more other dibasic acids selected from the group consisting ofsaturated aliphatic dibasic acids and aromatic dibasic acids, and has anumber average molecular weight of between 1500 and 3500, (2) from 2 to20 moles, per mole of the aforesaid polyester diol of an aliphatic diolOpt al y w tain ng a vlen gr p or a y pha ic diol, which diol has notmore than 20 carbon atoms and (3) from 96 to 100 moles, per 100 moles ofthe total weight of the foregoing diols, of an aliphatic orcycloaliphatic diisocyanate having from 4to 24 carbon atoms, which mayoptionally contain aromatic nuclei provided the latter are separatedfrom the isocyanate groups by at least one methylene group. I

This invention relates to the manufacture of novel synthetic elastomers,and more particularly to such elastome'rs as consist of segmentedpolyester-urethanes with aliphatic urethane segments and are capable ofbeing melt-spun into filaments.

For many years synthetic rubbers have been manufactured includingpolyester-urethane elastomers but it is difficult or impossible todissolve these elas tomers, which are cross-linked (cured), withoutdegradation, and such solutions as are obtainable cannot be solutionspun into filaments. Nor can filaments be made by melt-spinning theelastomers. Elastic filaments could only be formed therefrom bymechanically cutting up thin sheets into narrow strips, but such aprocess has drawbacks; in particular it is not possible to producefilaments of low denier, i.e. much below 500.

In the last decade much research has been carried out on the developmentof synthetic elastome rs capable of being solution spun into elasticfilaments possessing desirable textile properties. Such elasticfilaments possess an extensibility of over 100%, a low initial modulusand a high percentage elastic recovery. The terms extensibility, initialmodulus and elastic recovery are defined below. Some of the aforesaidresearch had been directed to the improvement of elastornerswhich arepolyester-urethanes. U.S. patent specification 3,097,- 192, for example,describes 'malr in g polyester-urethaneureas from a polyester, a molarexcess of an aromatic diisocyanate and a diamine; thepolyester-urethane-ureas can be solution spun into elastic filaments bymeans of Wet or dry spinning. Such elastic polymers comprise segmentsconsisting of a low molecular weight polymer which if fully polymerisedso as to constitute a fibre-forming homopolymer would possess arelatively high melting point, together with segments which cansimilarly be regarded as derived from a fully polymerised homopolymer ofrelatively low melting point! The former segments are frequently calledhard segments and the latter soft segments, as, for example, in thearticle by W. H. Charch and I. C. Shivers entitled ElastomericCondensation Block Copolymers and to be found in the Textile ResearchJournal for July 19.59. i

Attempts have also been made to produce synthetic elastomers which canbe elt-sputum textile filaments for the process' of melt-spinning iswell known to possess nurnerous advantages over that ofsolutionspinning. Thus Belgian patent specification No. 619,994 it proposed tomake melt-spinnable polyurethanes by the reaction of ahydroxyl-terminated polyester or copolyester (i.e. a'diol) having anaverage molecular weight not exceeding 1400 with an organic diisocyanateand 'a 'chain extender, preferably a dihyd ric alcohol elg.butanediol-IA the molar excess of diisocyanate to total diol, rangingfrom 1.1451 to 1.02: 1. TheBelgian specification mentions alicyclic andaliphatic diisocyanates such as tetramethylene diisocyanate orhexamethylene diisocyanate but gives no examplesof the use thereof. Infact processes are described wherein a molar excess of diisocyanateisheated with a hydroxylte i ed P l ster and uc ocesse ould be l 9 mWith. an. p ati d s pyana e beaus nde these ,wnq i n ell n oc rs.- N ikenew be n oun at no e mel -sn nna e po y- =st 1 1 a es mp ove r pe ti scan he. made f om a y oisy etm a d opo st r o mo ecu ar weigh greaterthan 1500, a dihydric alcohol and an aliphatic or cycloaliphaticdiisocyanate provided the diisocyanate is neither employed in molarexcess nor allowed to be present molar excess at any time during thereaction; A1 though the "above Belgian specification states that the.use or polyestersofhigher molecuiar weight yields filaments ofiiife'rior properties, applicants have found that by raising the'molecular weight of the polyester better values for work recovery andstress decay (as defined below) are obtained."Moreover the elasticfilamentsof polyesterurethanes derived from aliphatic diisocyanates aredistinguished from the elastic filaments of those based on aromatic"diisocyanatesby possessing advantageous properties. Thus the formerpolyester-urethane filaments re} tain their elastic properties andwhiteness to a greater extent when exposed to lig ht than do the latter;moreover the latter became yellow when submitted to bleaching by hotaqueous sodium chlorite and also on ageing, whereas the former do not.The degree of resistance to'light and bleaching is determined by meansof tests which maybe defined in the following manner.

Light resistance test The filaments are, Wound on a frame and exposed tolight fram a Xenon Arc for 300 hours. The elastic properties and colourof the filaments are determined before and after the exposure.

Bleaching resistance test The filaments are immersed for a period of 45minutes in an aqueous solution containing 0.1% by weight of sodiumchlorite and 0.5 cc. per litre of glacial acetic acid maintainedat C. isW V The colour of the filaments is determined before and after thebleaching treatment. a I

With regard to the polyester-urethanes of Belgian patent specificationNo. 619,994 therefore, not only do the present polyesterurethanes differin respect of the molecular Weight of the polyester used and theproportion and chemical constitution of the diisocyanate employed, butthe elastic filaments made'by' mel pinning the presentpolyester-urethanes possess superior textile properties. A

Definitions of properties of filaments.Extensibility By extensibility ofthe filaments is meant the length by which they can be extended beforethey break expressed as a percentage of their original length.

Tenacity The breaking load of the filaments expressed in grams perdenier.

Initial modulus By initial modulus of the filaments is meant thequotient obtained by dividing the specific stress by the strain, whenthe strain is an extension of 1 percent of the original length.(Specific stress is defined at page 138 of the Textile Terms andDefinitions, 4th edition, published by the Textile Institute,Manchester, and may be expressed in grams per denier.)

Elastic recovery The elastic recovery of the filaments is expressed bythe fraction obtained by dividing the length by which the filaments areextended on the application of a stress thereto, into the length bywhich they contract on removal of the stress therefrom. The fraction iscommonly expressed as a percentage.

Work recovery The work recovery of the filaments is expressed by thefraction obtained by dividing the energy or work expended in stretchingthe said filaments by applying a stress thereto into the energy or workrecovered when the said filaments retract to their original dimensionson release of the stress. The fraction is commonly expressed as apercentage.

Stress decay The stress decay of the filaments is expressed by thefraction obtained by dividing the stress necessary to extend thefilaments by a selected percentage of their original length, into thestress required to produce the same extension at the end of a selectedtime, the said extension being maintained constant during the Wholeofthe time. The fraction is commonly expressed as a percentage.

Stick temperature The lowest temperature at which the filaments adhereto a hot smooth surface when brought into contact therewith.

Inherent viscosity The inherent viscosity is defined as being twice thenatural logarithm of the viscosity at 25 C. of a solution of /2 weightby volume of the polyester-urethane dissolved in meta-cresol, divided bythe viscosity of the metacresol at the same temperature.

Vicat softening point The Vicat Softening Points alluded to have beendetermined by a penetrometer similar to the apparatus described by Edgarand Ellery at page 2638 of Journal of the Chemical Society 1952.

Accordingly the invention consists of a process for the manufacture ofsynthetic polyester-urethane elastomers capable of being melt-spun intofilaments, comprising bringing about by the application of heat aninteraction between (1) a diol which is a hydroxyl-terminated linearcopolyester derivable from one or more aliphatic or cycloaliphaticglycols having from 2 to 20 carbon atoms, and adipic acid optionallytogether with one or more other dibasic acids selected from the groupconsisting of satugoing diols, of an aliphatic or cycloaliphaticdiisocyanate having from 4 to 24 carbon atoms, which may optionallycontain aromatic nuclei provided the latter are separated from theisocyanate groups by at least one methylene group.

Examples of the reagents which may be employed in the present processare as follows:

Hydroxyl-terminated linear copolyesters copolyesters derived from thesubjoined glycols and dibasic acids in the ratios by Weight quoted andhaving the molecular Weights (M.W.) stated.

Glycols Ratio Dlbaslc acids Ratio M.W.

Ethylene glycol, pro- 7:3 Adlplc 1, 640

pylene glycol. Ethylene glycol, 2,3- 7:3 .do 1, 550

butanediol. Ethylene glycol, 1,3- 7:3 .....(10 1, 550

butanediol. Ethylene glycol, 1,3- 7:3 do 1, 540

dihydroxy-2,2-dimethylpropane. Ethylene glycol Adiplc, succlnic..- 3:11, 560 Ethylene glycol Adipic, phthalic. 8:1 1, 550 Ethylene glycol, 13-7:3 Adlpic 1, 650

dihydroxy-2,2-diethylpropane. Ethylene glycol, 1,4- 7:3 dc 1, 600

butanediol. Ethylene glycol, 2,5- 7:3 .-do 1, 550

hexanediol. Ethylene glycol, 1,3-di- 7:3 do 2, 490

hydroxy-2,2,4-trlmethylpentaue. Ethylene glycol, pro- 7:3 Glutaric 1,650

py ene glycol.

Do 7:3 Sebaclc 1, 550 Ethylene glycol, trl- 7:3 Adiplc 1,630

methylene glycol.

The hydroxyl-terminated linear copolyester may be prepared from therequired glycol and dibasic acid by conventional methods, i.e. by theuse of a moderate excess, eg. 10 molar percent of the glycol. In placeof the acid the acid chloride may be employed. It is also possible touse the methyl ester of the dibasic acid, that is, to make the polyesterby a process of ester interchange but this method requires the use of acatalyst and it is preferred that no catalyst shall have been employedin making the copolyesters used as reagents in the present invention.This is because the presence of even small quantities of catalysts,which are difiicult or impossible to remove, causes discoloration of thepolyester-urethane finally obtained. Such discoloration is unacceptablein commercial textile filaments, unless the latter are required to bedeeply coloured. It is therefore normally essential to use polyesters inthe manufacture of which no catalyst has been employed.

Aliphatic dials optionally containing arylene groups and cycloaliphaticdials 1,4-butanediol 1,6-hexanediol di 2-hydroxyethy1) -terephthalate di(4-hydroxy-n-butyl) -terephthalate trans-l,4-dihydroxycyclohexanecis-l,4-dihydroxycyclohexane 2,2,4,4-tetramethyl-cyclobutane-1,4-diol1,4-di(hydroxymethyl)benzene l,4-di(2-hydroxy-n-propyl)-benzenetrans-2,5-di(hydroxymethyl)-1,4-dioxancis-l,4-di(hydroxymethyl)cyclohexane transl ,4-di (hydroxymethyl)cyclohexane l,4-di-beta-hydroxyethoxybenzene2,2-bis-4-beta-hydroxyethoxyphenylpropane Aliphatic and cycloaliphaticdiisocyanates hexamethylene diisocyanatetrans-1,4-di-isocyanate-cyclohexane tetramethylene diisocyanatemeta-xylylene diisocyanate para-xylylene diisocyanate pentamethylenediisocyanate trans-l,4-bis-isocyanate-methyl-cyclohexane decamethylenediisocyanate 2,2-di(4'-isocyanato-cyclohexyl)-propanedi-(4-isocyanato-cyclohexyl) -methane In the manufacture of the presentsynthetic elastomers the diols and diisocyanate may be brought togetherin any convenient manner provided that no molar excess of diisocyanateover the total weight of diols present occurs under reaction conditions,that is to say, for example, at a temperature high enough for reactionto take Place. One method of proceeding is to mix the copolyester diolwith the low molecular weight diol, heat the mixture up to, say, 100 C.and add the diisocyanate, whilst the temperature is raised further sothat the polyester-urethane formed does not solidify. The reaction ispreferably carried out under an inert atmosphere, e.g. nitrogen, toprevent oxidation of the polymer occurring. Eificient mechanical mixingof the reagents is highly desirable. Another method of proceeding is toadd part of the diisocyamate to the copolyester diol. The diisocyanatemay amount to half or two thirds mole per mole of the copolyester, forinstance. The low molecular weight diol is then added followed by theremainder of the diisocyanate.

The low molecular weight diol which provides the hard segment in thepresent polyester-urethanes is employed, as already stated, in a molarexcess over the copolyester diol which provides the soft segment, themolar ratio of the two diols ranging from 2:1 to 20:1. The filamentsspun from the polyester-urethanes possess the most desirable textileproperties, however, when the aforesaid molar ratio is from 3:1 to 9:1.

Catalyst such as the following may, if desired, be included in thereaction mixture to further the reaction of the diisocyanate.

dibutyl stannic dilaurate dimethylcyclohexylamine sodium ethoxide sodiumphenate ferric acetylacetonate Moreover the manufacture of thepolyester-urethane can be carried out in solution. Suitable solvents forthis purpose'are:

N,N-dimethylacetamide pyridine dimethylsulphoxide mixed with an equalvolume of methyl isobutyl ketone N,N-dimethylformamidehexamethylphosphoramide tetramethylene sulphone The presentpolyester-urethanes can be manufactured in solution and the latterdirectly spun into filaments by conventional dry or wet spinningmethods. The solutions of the polyester-urethanes can also be cast intofilms. As

already indicated the textile filaments are, however, preferably made bymelt-spinning in which case no solvent is required. The filaments can bedrawn in the solid state (a process often termed cold drawing) althoughthis is not essential and if the maximum extensibility is required nodrawing should be carried out.

Among the reagents employed in making the present polyesterurethanesthere may be included pigments, plasticisers, delustrants orstabilisers.

The polyester-urethanes of this invention preferably possess a molecularweight corresponding to an inherent viscosity of from 0.5 to 1.5.

The invention includes melt-spinning the above novel syntheticpolyester-urethanes into filaments and the filaments so-obtained. Thelatter possess excellent elasticity, and do not discolour when exposedto a Xenon are or bleached with sodium chlorite in accordance with theLight Resistance and Bleaching Resistance Tests hereinbefore defined.The filaments likewise possess good elastic recovery and good workrecovery, frequently exhibiting an Elastic Recovery from 50% extensionof at least and a Work Recovery from 50% extension of at least 75%. Thefilaments are usually submitted to a hot wet treatment, e.g. withboiling water during dyeing or scouring before commercial use and havetherefore in the following examples been given a treatment with boilingwater before the physical properties were determined in order to obtainmore comparable results.

The present polyester-urethanes are advantageously distinguished fromother synthetic elastomers by the ease with which they can be melt-spuninto filaments which exhibit no tendency to stick together andconsequently do not need dusting with talcum powder. Furthermore thesenovel polyester-urethane filaments are superior to known elastomericfilaments having similar physical properties in that they do notdiscolour when submitted to the Light and Bleaching Resistance Testshereinbefore defined. The filaments are suitable for so-calledfoundation garments such as corsets, in elastic outerwear, for instancesweaters, ski-trousers, also in surgical elastic hosiery and bandages.Other uses comprise woven or knitted swimwear, hosiery, brassieres, andpyjamas. The present filaments are likewise adapted for similarwidespread application in the form of staple fibres, especially whenblended with e.g. wool, cotton, polyhexamethylene adipamide. The novelpolyester-urethane filaments of this invention may be fabricated intocomposite elastic yarns by introducing them as continuous filamentstogether with one or more rovings of staple fibres e.g. polyethyleneterephthalate, wool or cotton fibres, into a conventional spinning ordrafting frame. In the form of fibres the present polyesterurethanes canbe used in making non-woven fabrics or, blended with wool, for weavingcloth suitable for mens suits.

In the following examples which are for the purpose of illustrating, notlimiting, the invention, the parts are parts by weight.

Example 1 54.7 parts of a hydroxy-terminated copolyester derived fromethylene and propylene glycols in a molar ratio of 7:3 and adipic acidand having a molecular weight of 1640, are mixed with 14.0 parts of1,4-butanediol. The mixture is heated for 30 minutes at C. in anatmosphere of nitrogen with continuous stirring.

To the above mixture of diols there are added with stirring during 5minutes 15.7 parts of hexamethylene diisocyanate. A further addition of15.7 parts of hexamethylene diisocyanate is then made during 70 minuteswhilst the temperature is gradually raised at 200 C., the reac tionmixture being constantly stirred. The mixture is stirred at the sametemperature for 25 minutes longer and then cooled under the atmosphereof nitrogen.

The resulting polyester-urethane has an inherent viscosity of 0.59 and aVicat softening point of C.

The polyester-urethane is melt-spun at a temperature of -195 C. into 10filaments of total denier 319. The lO-filament yarn after treatment withboiling water has the following properties:

Tenacity gram/den 0.43

Initial modulus gram/den 0.24 Stress decay at 25% extension:

15 minutes percent 25.2

16 hours do 37.6

Elastic recovery from 50% extension d0 98 Work recovery from 50%extension do 75 Example 2 The manufacture of polyester-urethanedescribed in Example 1 is repeated except that the 58.8 parts ofcopolyester there employed are replaced by 58.8 parts of ahydroxyl-terminated copolyester derived from ethylene glycol and1,4-butanediol in a molar ratio of 7:3 and adipic acid and having amolecular weight of 1600, the

7 weight of 1,4-butanediol is reduced from 14.0 to 12.2 parts and thetotal Weight of hexamethylene diisocyanate used is 28.3 instead of 31.4parts.

The properties of the polyester-urethane obtained are:

Inherent viscosity 0.88 Vicat softening point C 164 The yarn melt-spuntherefrom and cold drawn (at C.) to three times its original length; itis then treated with boiling water and has the properties listed below:

Stress decay at 25% extension:

15 minutes percent 22.2

16 hours do 34.5

Elastic recovery from 50% extension do 98 Work recovery from 50%extension do.. 94

Example 3 Example 1 is repeated except that the reagents thereinemployed are replaced by the following:

The copolyester is derived from ethylene glycol together with adipic andsuccinic acids in a molar proportion of 3 to 1 and has a molecularweight of 1560, 58.7 parts are taken and mixed with 12.2 parts of1,4-butanediol, 291 parts of hexamethylene diisocyanate are employed (intwo equal portions).

The properties of the resulting polyester-urethane are:

Inherent viscosity 1.14 Vicat softening point C-.. 160

The yarn melt-spun therefrom has after treatment with boiling Water thefollowing properties:

Stress decay at 25% extension:

15 minutes percent 23.4

16 hours do 37.4

Elastic recovery from 50% extension do 94 Work recovery from 50%extension do 93 Example 4 Example 3 is repeated except that thecopolyester is replaced by 58.4 parts of one derived from ethyleneglycol and 1,3-dihydroxy-2,2-dimethylpropane in the molar pro portion of7 to 3 and adipic acid and has a molecular weight of 1540.

The properties of the polyester-urethane are:

Inherent viscosity 0.60 Vicat softening point C 165 Thepolyester-urethane is melt-spun in the manner described in Example 1 andthe resulting filaments drawn to four times their original length andtreated with boiling water.

They are found to possess the following properties:

A polyester-urethane elastomer possessing greater extensibility can beobtained by increasing the molecular weight of the copolyester andaltering the quantities of reagents as follows:

Parts Copolyester 84.0 Butane diol 12.9 Diisocyanate 32.2

The resulting polyester-urethane has an inherent viscosity of 0.85 and aVicat softening point of 140 C. Its extensibility is 460%.

Example 5 A polyester-urethane is made in the manner described inExample 1, except that the copolyester is replaced by 58.9 parts of acopolyester derived from ethylene glycol and trimethylene glycol in amolar proportion of 7:3 and adipic acid, and having a molecular weightof 1631. 29.7 parts of hexamethylene diisocyanate are employed. Thepolyester-urethane has an inherent viscosity of 1.03 and a Vicatsoftening point of 159 C. The polymer is melt-spun into filaments andthe latter drawn to three times their original length. The filaments onbeing extended by 50% exhibit an Elastic Recovery of 99% and a workrecovery of 79%.

Example 6 57.6 parts of the copolyester used in Example 2 are heated to100 C. under an atmosphere of nitrogen, and 2.6 parts of hexamethylenediisocyanate added during 15 minutes. Efficient stirring is maintainedcontinuously during the manufacture of the polyester-urethane. Thereaction mixture is heated to C. and maintained thereat for 30 minutes.The temperature is then lowered to 60 C. and 12.2 parts of1,4-butanediol are added during 10 minutes. The mixture is heated to 100C. during 15 minutes and 25.2 parts of hexamethylene diisocyanate aregradually added during 60 minutes while the temperature is furtherraised to C. so that the reaction mixture remains molten. Thetemperature is kept at 180 C. for 30 minutes and the polyester-urethanethen cooled. Ithas an inherent viscosity of 0.65 and a Vicat softeningpoint of 171.

The polymer is melt-spun at 169 C. yielding filaments which afterdrawing to three timestheir original length and boiling in water possessthe following properties Stress decay at 25 extension:

15 minutes percent.... 25.0

16 hours o 36.2

Elastic recovery from 50% extension do 99 Work recovery from 50%extension do 80 Example 7 Example 8 57 parts of a hydroxyl-terminatedpolyester derived from ethylene glycol and 1,3-dihydroxy-2,2-dimethylpropane in the molar ratio of 7 to 3 and adipic acid and having amolecular weight of 1540, are mixed with 18.95 parts of1,4-di(fl-hydroxyethoxy) benzene at 110 in an atmosphere of nitrogen andstirred for 30 minutes.

To the above mixture of diols there are added with stirring 15 partshexamethylene diisocyanate during 15 minutes while the temperature israised to 180. A further 8.18 parts of hexamethylene diisocyanate areadded during 60 minutes while the temperature is gradually raised to200. The mixture is stirred at the same temperature for 40 minuteslonger and then cooled under the atmosphere of nitrogen.

The resulting polyester-urethane has an inherent viscosity of 0.86 and aVicat softening point of 179.

The polyester-urethane is melt-spun at 215 and after treatment withboiling water the yarn has the following properties:

Percent Stress decay at 25% after 15 minutes 47 Elastic recovery from100% extension 95 Work recovery from 100% extension 75 Example 60 partsof a hydroxyl-terminated polyester derived from ethylene glycol and1,3-dihydroxy-2,2-dimethylpropane in the molar proportion 7 to 3 andadipic acid and having a molecular weight of 1656 are mixed with 15.3parts p-xylylene glycol at 110 in an atmosphere of nitrogen and stirredcontinuously for 30 minutes.

To the above mixture of diols there are added with stirring 12 parts ofhexamethylene diisocyanate over minutes while the temperature is raisedto 180. A further 11.7 parts hexamethylene diisocyanate is added over 60minutes while the temperature is raised to 200. The mixture is stirredat the same temperature for 30 minutes longer and then cooled under theatmosphere of nitrogen.

The resulting polyester-urethane has an inherent viscosity of 0.56 and aVicat softening point of 180. The polymer is melt-spun at 203 to giveyarn which after treatment with boiling water has the followingproperties.

Percent Stress decay at extension (after 15 minutes) 31 Elastic recoveryfrom 100% extension 87 Work recovery from 100% extension 50 Example 11The p-xylylene glycol of Example 10 is replaced by 15.7 parts ofcis/trans-1,4-di(hydroxymethyl) cyclohexane. The resultingpolyester-urethane has an inherent viscosity of 0.59 and a Vicatsoftening point of 151. It is melt-spun at 182 C. into yarn having goodelastic properties.

Example 12 36 parts of a hydroxyl-terminated polyester derived fromethylene glycol and 1,3-dihydroxy-2,2-dimethylpropane in the molarproportion of 7 to 3 and adipic acid and having a molecular weight of2028 are mixed with 4.95 parts of butane-1,4-diol at 110 C. in anatmosphere of nitrogen and stirred together for minutes.

To the above mixture of diols there are added with stirring 19.05 partsof trans, trans-di(4-isocyanatocyclohexyl) methane during 75 minutesWhile the temperature is gradually raised to 200 C. The mixture isstirred at 200 C. for a further 40 minutes and then cooled.

The resulting polyester-urethane has an inherent viscosity of 0.96 and aVicat softening point of 193 C.

Example 13 The proportions of the reagents employed in Example 12 arealtered to the following:

Di(isocyanatocyclohexyl)methane 12.32

10 'A polyester-urethane having an inherent viscosity of 0.64 and aVicat softening point of 172 C. is obtained. It is melt-spun at 205 togive yarn having the following properties.

Percent Elastic recovery from 100% extension 96 Work recovery from 100%extension 78 Example 14 35 parts of a hydroxyl-terminated polyesterderived from ethylene glycol and 1,3-dihydroxy-2,Z-dimethylpropane inthe molar proportion of 7 to 3 and adipic acid and having a molecularweight of 2028 are mixed with 4.95 parts of butane-1,4-diol at 110C. inan atmosphere of nitrogen and stirred together for 30 minutes.

To the above mixture of diols there are added with stirring 19.05 partsof di(4-isocyanato-cyclohexyl)rnethane (a mixture of the steric isomers)during 75 minutes while the temperature is gradually raised to 200 C.The mixture is stirred at this temperature for a further 40 minutes andthen cooled.

The resulting polyester-urethane has an inherent viscosity of 0.50 and aVicat softening point of 141 C.

The polymer is melt-spun at 188 C. giving yarn with the followingproperties:

Percent Elastic recovery from 100% extension 89 Work recovery from 100%extension 56 Example 15 Percent Elastic recovery from 100% extension 90Work recovery from extension 55 Example 16 Example 15 is repeated exceptthat the 17.3 parts of di(4-isocyanato-cyclohexyl)-methane (mixed stericisomers) are replaced by the same quantity of m-Xylylene diisocyanate.The resulting polyester-urethane has an inherent viscosity of 0.66 an aVicat softening point of 127 C.

Example 17 Example 14 is repeated except that the quantity ofbutane-1,4-diol is reduced from 4.95 to 3.8 parts and thedi(isocyanato-cyclohexyl) methane replaced by 11.2 parts of p-xylylenediisocyanate. The resulting polyester-urethane has an inherent viscosityof 0.44 and a Vicat softening point of 174 C.

What I claim is:

An elastomeric filament consisting of a polyester-urethane obtainable byheating together (1) a diol being a hydroxyl-terminated linearcopolyester with a number average molecular weight between 1500 and 3500and being a reaction product of aliphatic and cycloaliphatic glycolshaving from 2 to 20 carbon atoms and adipic acid optionally togetherwith other dibasic acids selected from the group consisting of saturatedaliphatic dibasic acids and aromatic dibasic acids, .(2) from 2 to 20moles, per mole of the aforesaid polyester diol, of a diol having notmore than 20 carbon atoms and selected from the group consisting ofaliphatic diols optionally containing arylene groups and cycloaliphaticdiols and (3) from 96 to 100 moles, per 100 moles of the total weight ofthe foregoing diols, of a diisocyanate having from 4 to 24 carbon atoms,selected from the group consisting of aliphatic and cyclo- 1 1 aliphaticdiisocyanates and optionally containing aromatic nuclei provided thelatter are separated from the isocyanato groups by at least onemethylene group, which filament has an Elastic Recovery from 50%extension of at least 95%, a work recovery from 50% extension of atleast 75% and does not discolour when exposed to a Xenon Arc or bleachedwith sodium chlorite in accordance with the light resistance andbleaching resistance tests in which the filaments are immersed for aperiod of 45 minutes in an aqueous solution containing 0.1% by weight ofsodium chlorite and 0.5 c.c. per litre of glacial acetic 12 acidmaintained at 85 C. and the colour of the filaments is determined beforeand after the bleaching treatment.

References Cited UNITED STATES PATENTS 2,871,218 1/ 1959 Schollenberger26075 3,174,949 2/ 1965 Harper 2607S 3,233,025 2/1966 Frye et a1 2607510 DONALD E. CZAJA, Primary Examiner.

G. W. RAUCHFUSS, 111., Assistant Examiner.

